Apparatus for the aeration of water comprising a power source which drives a shaft to which a mixing device is affixed are well known, as can be seen from the Belgian patent 893.687.
European patent 0.366.644 describes this type of aerator in a form which can also be used as a mixer, whereby the power source is secured to a structure comprising two floats positioned one on top of the other and whereby the lower float can be immersed by the introduction of ballast.
The power source drives a helical propelling device which can operate in both directions of rotation. This apparatus can be used as an aerator when the top float is positioned above the surface of the water (The unit is then actually floating on the bottom float). If the apparatus floats on the top float and the direction of rotation is reversed, this apparatus can be used as a mixer.
Because of the twin floats and the associated manufacturing and operation costs there is a pressing need for a simpler apparatus which can be used both as a mixer and as an aerator.
A detailed investigation has been carried out to find an as simple apparatus design as possible, starting from a conventional mixer and from the apparatus described in EP 0.366.644, in which all the components have undergone an in-depth analysis and in which all possible parameters of each component have been studied during usage.